Biomimetic Recognition and Optical Sensing of Carboxylic Acids in Water by Using a Buried Salt Bridge and the Hydrophobic Effect

Abstract

Buried salt bridges widely exist in protein structures but are rarely used in synthetic systems for molecular recognition in water.B ym imicking the binding pocket of bioreceptors,w ed esigned and synthesized ap air of endofunctionalizedm acrocyclic hosts with secondary ammonium groups in ah ydrophobic cavity.W ef ound that these macrocycles are able to selectively recognizecarboxylic acids in water through salt bridges and the hydrophobic effect. Moreover,i t was demonstrated that these macrocyclic receptors can be used in circular-dichroism-based optical chirality sensing of chiral carboxylic acids and fluorescent sensing of phenylpyruvic acid-a biomarker for phenylketonuria. This researchs howcases that buried salt bridges can be effectively used by endofunctionalizedm acrocyclic hosts for molecular recognition in water,w here solvent screening on polar noncovalent interactions is high.

An Adaptable Water-Soluble Molecular Boat for Selective Separation of Phenanthrene from Isomeric Anthracene

“…In many cases, the binding site changes its conformation to perfect the fit of incoming substrates . Artificial molecular systems that undergo induced fit guest binding are challenging to design and are rare in the literature . Molecular receptors based on supramolecular self-assembly have emerged as a promising area in this regard .…”

When Molecules Meet in Water‐Recent Contributions of Supramolecular Chemistry to the Understanding of Molecular Recognition Processes in Water

“…In the case of 21, large positive entropic terms of complex formation suggest that binding benefits from the release of water molecules from the receptor cavity. [87] These and further examples [88][89][90][91][92][93] illustrate that ionic interactions in water contribute to the stability of host-guest complexes. The high stabilities observed for certain complexes, the pronounced exothermicities associated with complex formation, and some binding selectivities indicate, however, that other types of interactions, including those mediated by the solvent, also influence binding, sometimes even to a larger extent than salt bridge formation.…”

“…The Jiang group subsequently demonstrated that naphthotubes bind a variety of polar guests in water, [185] including surrogates of nerve agents. [186] In addition, naphthotubes can be used for the chiroptical sensing of epoxides, alcohols, [187] and carboxylic acids, [92] and for the removal of micropollutants from water, rendering them potentially useful for practical applications. [188] Other macrocyclic tetralactams in which converging hydrogen bond donors and two hydrophobic anthracene units mediate guest binding in water are receptor 50 a, described by…”